1. Field of the Invention
The present invention relates to signal processing, and more particularly to an adaptive multi-sensor array and method thereof.
2. Discussion of the Related Art
Microphone arrays are used in various devices, such as hearing aids and speech recognition applications. One problem with these devices is noise, and the elimination of noise from a signal received by the microphone array. In the field of hearing aids, there exist several proposed solutions. The proposed solutions can be divided into three classes of microphone array schemes: side-lobe canceller, beamformer, and differential microphone array (DMA). Many of the known adaptive methods for reducing noise address the first two classes, side-lobe cancellers and beamformers. However, few works address the adaptability of the differential microphone array scheme.
Two works that discuss differential microphone arrays are H. Teutsch and G. W. Elko, “First and second-order adaptive differential microphone arrays”, 7th International Workshop on Acoustic Echo and Noise Control, pages 35–38, 2001; and U.S. Pat. No. 5,473,701 to J. Cezanne and G. W. Elko entitled “Adaptive Microphone Array”. The differential microphone array works implement an adaptation by minimizing an output variance.
The proposed solutions implementing differential microphone arrays utilize an optimization criterion, which is a total output power or energy. The criterion is of the form T1+T2 where T1 is the output energy due to the signal, and T2 the output energy due to the noise. Thus, the optimization problem is: min(T1+T2)
This optimization problem has an inherent limitation; when the source position is in a null-allowed region, then either no processing is done, or if the optimization problem is solved, it cancels a target source.
Similarly, a directivity index of the prior art differential microphone array work is always maximal for theta=0. Thus, it is an end-fire array and there is no adaptability when the source moves.
Additionally, a parameter beta is implemented that adjusts the directivity pattern.
Therefore, a need exists for an adaptive multi-sensor array.